Results

Results of the BUN test are measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) internationally. In general, around 6 to 24 mg/dL (2.1 to 8.5 mmol/L) is considered normal.

But normal ranges may vary, depending on the reference range used by the lab and your age. Ask your doctor to explain your results.

Urea nitrogen levels tend to increase with age. Infants have lower levels than other people do, and the range in children varies.

Generally, a high BUN level means your kidneys aren't working well. But elevated BUN can also be due to:

• Dehydration, resulting from not drinking enough fluids or for other reasons
• Urinary tract obstruction
• Congestive heart failure or recent heart attack
• Gastrointestinal bleeding
• Shock
• Severe burns
• Certain medications, such as some antibiotics
• A high-protein diet

If kidney damage is a concern, ask your doctor what factors may be contributing to the damage and what steps you can take to try to control them.